JP2006090430A - Cross shaft coupling - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a maintenance-free cross shaft coupling for further improving the steering performance and feeling and aging stability of a steering device. <P>SOLUTION: The cross shaft coupling 1 comprises a bearing filled with grease which contains (a) puffing agent consisting 12-24 carbon-number fatty acid having hydroxyl groups in molecules and lithium salt of 2-12 carbon-number aliphatic dicarboxylic acid, (b) base oil having a kinetic viscosity of 60-200mm<SP>2</SP>/s at 40°C and containing as essential components, mineral oil having a kinetic viscosity of 300-500mm<SP>2</SP>/s at 40°C and synthetic hydrocarbon oil having a kinetic viscosity of 20-300mm<SP>2</SP>/s at 40°C, (c) dithiocarbamic acid salt of tellurium, and (d) phosphate. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a cross joint for use in a vehicle steering device or the like.

  In general, in a vehicle steering apparatus, for example, a cross that includes a pair of yokes and a cross-shaped spadder between an upper shaft and a low shaft of a steering shaft and transmits torque while rotating at a predetermined bending angle. A shaft coupling is inserted.

  As this cross shaft joint, for example, the spider shaft part of the spider is swingably fitted into the bearing hole of the yoke via a needle bearing including a plurality of roller rolling elements, and formed on the axis of the spider shaft part. There is known a configuration in which a spherical protrusion formed on the axial center of the inner surface of the needle bearing cup is fitted and pressed into the conical hole (see Patent Document 1). Thereby, even if vibration is transmitted from the wheel, the minute gap between the spider shaft and the needle bearing is maintained uniformly, and the generation of noise due to the interference between the two is prevented.

  However, in the above cross shaft joint, when the dimensional accuracy of each part is low, when the spider is assembled into the yoke, the spherical protrusion on the inner surface of the needle bearing cup is inserted into the conical hole of the spider shaft with an appropriate preload. Since it becomes difficult to contact, the minute clearance between the spider shaft and the needle bearing cannot be maintained uniformly, and abnormal noise and vibration (rattle) may occur due to interference between the two. Steering also serves as a sensor that senses the driver's sense of road surface conditions and vehicle behavior, such as the contact between the tire and the road surface and the sense of self-alignment. Therefore, it is desirable that steering be less sensitive to noise and rattling. Therefore, the present applicant has previously proposed a cross shaft joint in which the end shaft portion of the spider is fitted into the bearing via a rolling element to suppress backlash (see Patent Document 2).

JP 2000-170786 A WO03 / 64877

  However, even in the cross shaft joint disclosed in Patent Document 2 by the present applicant, when the shimeshiro is excessive, a phenomenon (skew) occurs in which each needle is inclined with respect to the normal rotation axis and smooth rolling is inhibited. In particular, when the rotation angle is small and the direction is not constant as in a steering operation, a so-called harsh feeling is transmitted to the driver. Further, since the needle bearing to be incorporated is not equipped with a cage, iron powder is likely to be generated due to sliding friction, and the driver is likely to feel a so-called roughness.

  In addition, grease is sealed in the needle bearing for lubrication, but when iron powder enters the grease, the iron is ionized and acts on the thickener, increasing the consistency of the grease and improving the snake control. Decreases with time. Furthermore, since the needle bearing is assembled so that it cannot be detached / re-coupled, it cannot be lubricated and maintenance-free is also required. However, the cross-shaft joint is located close to the exhaust pipe on the rear side of the vehicle for handling the engine room. Since the grease is constantly exposed to high temperatures during operation, the grease is easily deteriorated by heat, and high temperature durability is important.

  Since the steering sensation of the steering system greatly affects the merchantability of the vehicle as a whole, there are particularly strong demands for reduction in gritty and roughness, stability over time, and maintenance-free. There is still room for improvement.

  Conventionally, compounds such as solid lubricants such as general molybdenum disulfide, sulfur, phosphorus, sulfur-phosphorus organic molybdenum, and organic zinc are known as extreme pressure agents. However, all of these compounds have strong chemical activity. When used alone, they have the effect of improving the lubricity of sliding parts in the short term. Although it does not cause seizure, smooth rotation tends to be impossible at an early stage. As a result, there was a problem that the smooth steering operation was hindered.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a cruciform joint that further enhances the operability and sensation of steering, the stability over time, and realizes maintenance-free operation. To do.

In order to achieve the above object, the cross joint of the present invention is configured such that a spider shaft is rotatably fitted in a bearing hole of a yoke via a bearing including a bearing cup and a plurality of rollers in the bearing cup. Thus, in the cross joint having a configuration in which a spider is fitted to the yoke, (a) a fatty acid having 12 to 24 carbon atoms having a hydroxyl group in the molecule and a lithium salt of an aliphatic dicarboxylic acid having 2 to 12 carbon atoms a thickening agent consisting of, containing as essential components a synthetic hydrocarbon oil of (b) mineral oil having kinematic viscosity of 300 to 500 mm ² / s at 40 ° C., a kinematic viscosity at 40 ℃ 20~300mm ² / s and a base oil is a kinematic viscosity at 40 ° C. is 60~200mm ² / s, and dithiocarbamates (c) tellurium, grease containing a (d) phosphoric acid ester Characterized by being sealed in the bearing.

  The cross shaft joint of the present invention is less likely to generate iron powder and contains grease containing an additive that suppresses the increase in consistency. Performance, sensation, and stability over time can be improved. In addition, since the grease base oil has excellent heat resistance, it is also excellent in high temperature durability and maintenance-free.

  Hereinafter, the present invention will be described in detail.

  In the present invention, the configuration of the cross joint itself is not limited. However, since the backlash is small, it is preferable that the needle bearing and the spider shaft portion are fitted with each other through a roller. Here, the needle bearing is a bearing in which a roller rolling element is interposed. FIG. 1 is a partial sectional view showing the first embodiment, and FIG. 2 is an enlarged view of a portion A. As shown in the figure, the cross joint 1 has a configuration in which a cross-shaped spider 2 is interposed between a pair of sheet metal yokes 7 and 8. The yoke 7 integrally has a cylindrical base portion 7a and a pair of arms 7b and 7b that extend in the axial direction from the cylindrical base portion and face each other in the diametrical direction. The cylindrical base portion 7 a is connected to the shaft 6 via a buffer portion 19. The buffer portion 19 includes an outer cylinder 21, an inner cylinder 20, and a rubber bush 9 made of rubber sandwiched between them. The inner cylinder 20 is externally fitted and fixed to the shaft 6, and the pin 10 is fixed to the inner cylinder 20. A female spline 25 is formed on the inner peripheral surface of the shaft 6. The yoke 8 forms a substantially cylindrical peripheral surface, and a base portion 8a having a pair of fastening portions opposed in a part in the circumferential direction and a pair of arms 8b extending in the axial direction and opposed in the diametrical direction are integrally formed. Has a joint function with the shaft.

  Circular bearing holes 18 are formed at the ends of the arms 7b of the yoke 7 and the ends of the arms 8b of the yoke 8 so as to face each other. The shaft portions 14 at the ends of the spider 2 are inserted into the bearing holes 18 of the yokes 7 and 8, respectively. The spider shaft portions 14 are respectively inserted into the corresponding bearing holes 18 of the yokes 7 and 8 via the needle bearings 3. It is supported rotatably.

  Since the configurations of the circular bearing holes 18 of the yokes 7 and 8 and the end shaft portion 14 of the spider 2 rotatably supported via the bearings 3 are all the same, in this specification, one of them will be described below. Will be described in detail.

  As shown in FIG. 2, the spider shaft portion 14 of the spider 2 is rotatably fitted in the bearing hole 18 of the yoke 7 via the needle bearing 3 including a plurality of roller rolling elements 12. A tapered chamfered portion 15 is formed around the outer periphery of the tip of the spider shaft 14. The chamfered portion 15 has an axial width L, and the tapered surface is set to form an angle θ of 0.5 ° to 1.2 ° with respect to the axial direction.

  The spider shaft portion 14 has an axial diameter of 9 to 10 mm, and its roundness and cylindricity are each 0.05 mm or less, preferably 0.002 mm or less. Further, the concentricity of the two shaft portions 14 facing each other is 0.05 mm or less, preferably 0.02 mm or less. The width L of the chamfered portion 15 is 0.5 to 3.0 mm, preferably 1.0 to 2.0 mm. The cross-sectional shape of the chamfered portion 15 is a straight line, but may be a curved shape.

  A thrust piece 17 is inserted into an axial hole 16 formed in the axial center of the spider shaft portion 14. A seal member 4 is provided on the outer periphery of the lower portion of the spider shaft portion 14.

  The thrust piece 17 is a pin made of a synthetic resin such as polyacetal resin or polyamide resin. When the thrust piece 17 is inserted into the axial hole 16, the end portion of the thrust piece 17 protrudes from the end surface of the shaft portion 14 and engages with the bottom surface of the bearing cup 11. When the bearing cup 11 is press-fitted, compressive elasto-plastic deformation is caused in the thrust piece 17, so that a preload toward the axial center is applied to the shaft portion of the spider 2, and the spider 2 sandwiched between the yokes 7b and 7b is pivoted. It can be held at a predetermined position in the direction.

  The needle bearing 3 includes a bearing cup 11, a plurality of roller rolling elements 12, a bearing cup 11 and a spider shaft portion 14, and is filled with grease 13 which will be described later. The bearing cup 11 is a bottomed cylindrical body and has an outer diameter of 15 to 16 mm. The bearing cup 11 is press-fitted into a circular bearing hole 18 formed in the arm of the yoke, and is prevented from being pulled out into the yoke 11 by a caulking portion 11a. A plurality of roller rolling elements 12 are interposed between the inner peripheral surface of the cylindrical portion of the bearing cup 11 and the outer peripheral surface of the spy shaft portion 14. With such a configuration, the spider shaft portion 14 is rotatably supported via the bearing 3 in the corresponding bearing hole 14 of the yoke arm.

  The roller rolling element 12 (hereinafter referred to as the roller 12) is formed into a shape in which the diameter R gradually decreases by a minute amount from the vicinity of the center to both ends. The amount of decrease in the diameter R is 0.004 to 0.022 mm at a position of 0.8 mm from the end face of the roller 12 toward the center. The roller 12 is set so as to be fitted with the spider shaft 14 and the needle bearing 3 in the vicinity of the center thereof, that is, in the region M of 13 to 70% of the entire length of the roller 12. For this reason, the load at the time of incorporating the spider shaft portion 14 into the needle bearing 3 can be reduced, and the assembling work is facilitated. The number of rollers 12 is 16 to 25, and the material is JIS SUJ1 to SUJ5. There is no limitation on the diameter and length.

  In this configuration, the chamfered portion 15 of the spider shaft portion 14 can be provided by cutting, but can be provided by simultaneous grinding with the spider shaft portion 14, and a high-accuracy one can be obtained at low cost.

  When the spider shaft portion 14 is assembled into the needle bearing 3, the tapered shape of the roller 12 and the chamfered portion 15 of the spider shaft portion 14 allow and guide each other, so that the roller 12, the bearing cup 11, The spider shaft portion 14 is hardly damaged, and even if it is attached, it can be kept to a minute one.

Further, since the spider shaft portion 14 is fitted together with the needle bearing 3 in the region M in the center portion of the roller 12, even if vibration is transmitted from the wheel, the spider shaft portion is near the both end portions of the roller 12. The minute gap formed between the bearing 14 and the roller 12 and between the inner diameter of the bearing cup 11 and the roller 12 is maintained uniformly, and the generation of abnormal noise due to the interference between the two can be prevented.
The steering device employing the cross shaft joint according to the present embodiment can be quickly steered when the steering wheel is steered during high speed running, and the steering stability is improved.

Furthermore, since the region M is smaller than the conventional roller, the increase in rolling resistance is small regardless of the fitting of the mesh, so that the bending torque is small and a smooth steering feeling can be obtained.
In addition, although the buffer part 19 was shown in this embodiment, you may assemble | attach a rubber coupling instead. In addition, a rubber coupling, a buffer portion of this embodiment, another type of buffer mechanism, a slide mechanism typified by spline fitting, or a displacement absorption at the time of collision may be applied to any part of the steering device to which this embodiment is applied. A mechanism or the like may be provided.

  Further, by using a cross shaft joint without backlash as in this embodiment and a slide mechanism without backlash, noise generation can be more effectively prevented in the entire system of the steering device. In addition, each cross joint has four needle bearings 3 and spider shafts 14, but the cross joint of the present embodiment is applied to at least one of them.

  Furthermore, the steering device that employs the cross joint of the present embodiment may be of any type such as hydraulic power steering, electric power steering.

  The cross joint can be the second embodiment shown in FIG. The cruciform joint of the second embodiment is substantially the same as the cruciform joint of the first embodiment, and in FIG. 3, the same members are denoted by the same reference numerals, and description thereof is omitted. This embodiment is different from the first embodiment in that the inward projection 23 formed on the inner center portion of the bottom surface of the bearing cup 26 of the needle bearing 22 and the end surface of the spider shaft portion 24 are in contact with each other. The present invention is applied to the cross joint 30 of the mold.

  Also in this cross shaft joint, the roller 12 has a shape in which the diameter R gradually decreases from the vicinity of the center to both ends, and a tapered taper chamfer with a width L is formed around the outer periphery of the tip of the spider shaft 24. The part 15 is formed, and the same effect as that of the cross joint of the first embodiment can be expected.

  In the second embodiment, a shell-type cross shaft joint is shown. However, the present invention can also be applied to a solid-type cross shaft joint.

  Further, the cross shaft joint may be the third embodiment shown in FIG. The cruciform joint of the third embodiment is substantially the same as the cruciform joint of the first embodiment. In FIG. 4, the same members are denoted by the same reference numerals, and the description thereof is omitted. As with the first embodiment, the roller 12 has a shape in which the diameter R gradually decreases from the vicinity of the center to both ends. This embodiment is different from the first embodiment in that the chamfered portion 15 of the spider shaft portion 14 is not provided, and the total amount of the roller 12 that can move in the axial direction of the spider 14 within the bearing cup 11 is reduced to 0. .6 mm. However, the total movable amount is at least 0.6 mm, and preferably 0.6 mm or more. That is, when the length of the roller 12 is T and the width of the inner space in the axial center direction of the spider shaft portion 14 in the bearing cup 11 is S, (ST) ≧ 0.6 mm.

  Therefore, if the roller 12 is disposed at the center of the bearing cup 11 in the axial direction of the spider 14, the roller 12 can move 0.3 mm in the axial direction of the spider 14.

  M is a range in which the spider shaft 14 is fitted together with the needle bearing 3 at the center of the roller 12. The surface roughness of the rolling surface 12 ′ of the roller 12 is an average roughness of 10 points according to JIS, which is about Rz 0.4 μm and the surface 14 ′ of the spider shaft 14 is about Rz 1 μm.

  In this configuration, the assembly time is longer than that of the cross joint of the first embodiment and the cost may be high. However, since the roller 12 does not contact the inner end surface of the bearing cup 11, the bending torque is smaller. Thus, a smooth steering feeling can be obtained.

  Hereinafter, the grease to be sealed will be described.

As the base oil of the grease, a mixed oil whose essential components are an inexpensive mineral oil and a synthetic hydrocarbon oil advantageous in heat resistance is used. Cross shaft joints are generally arranged close to the rear of the exhaust pipe in the handling of the engine room, and the needle bearings are often exposed to high temperatures. Therefore, since the grease cannot be supplied, durability at high temperature is also required for the encapsulated grease. Therefore, in the present invention, mineral oil having a kinematic viscosity at 40 ° C. of 300 to 500 mm ² / s, preferably 400 to 450 mm ² / s is used. This kinematic viscosity is considerably higher than the kinematic viscosity of a general mineral oil used for grease, thereby suppressing evaporation of the base oil as a whole. Therefore, if the kinematic viscosity at 40 ° C. is less than 300 mm ² / s, the effect of suppressing evaporation cannot be obtained. On the other hand, the kinematic viscosity at 40 ° C. is if exceeding 500 mm ² / s, startability at low temperatures deteriorates. The kind of the mineral oil is not particularly limited as long as it has the above kinematic viscosity, and a mineral oil that is usually used as a base oil for grease can be used. Among these, mineral oil purified by vacuum distillation, solvent history, solvent extraction, hydrocracking, solvent dewaxing, sulfuric acid washing, clay refining, hydrorefining, and the like is preferable.

As the synthetic hydrocarbon oil, one having a kinematic viscosity at 40 ° C. of ²⁰ to 300 mm ² / s, preferably 25 to 75 mm ² / s is used. When the kinematic viscosity at 40 ° C. is less than 20 mm ² / s, the amount of evaporation loss at high temperatures is large, and the grease solidifies at an early stage. On the other hand, when the kinematic viscosity at 40 ° C. exceeds 300 mm ² / s, sludge is generated or the startability at low temperatures is deteriorated. The type of the synthetic hydrocarbon oil is not particularly limited as long as it has the above kinematic viscosity, and a synthetic hydrocarbon oil usually used as a base oil for grease can be used. Preferred examples of the synthetic hydrocarbon oil include poly-α-olefins such as normal paraffin, isoparaffin, polybutene, polyisobutylene, 1-decene oligomer, 1-decene and ethylene co-oligomer, and hydrides thereof.

Although the base oil comprises a synthetic hydrocarbon oil with the above mineral oil as the essential, further kinematic viscosity at 40 ° C. as a base oil 60~200mm ² / s, preferably a feature that it is a 150 to 200 mm ² / s To do. When the kinematic viscosity at 40 ° C. as the base oil is less than 60 mm ² / s, the amount of evaporation loss at high temperatures is large, and the grease solidifies early. On the other hand, when the kinematic viscosity at 40 ° C. exceeds 300 mm ² / s, the start-up at a low temperature becomes worse. Therefore, the blending ratio of the mineral oil and the synthetic hydrocarbon oil is appropriately selected so that the kinematic viscosity is obtained when the base oil is used. However, in terms of cost, it is advantageous to increase the proportion of mineral oil, and from the viewpoint of heat resistance, it is advantageous to increase the proportion of synthetic hydrocarbon oil.

  In addition to mineral oil and synthetic hydrocarbon oil, the base oil can be blended with a lubricating oil that is usually used as a base oil for grease, if necessary. Aromatic, ester-based or ether-based synthetic lubricating oils as exemplified below are preferred. Examples of the aromatic oil include alkylbenzenes such as monoalkylbenzene, dialkylbenzene and polyalkylbenzene, and alkylnaphthalenes such as monoalkylnaphthalene, dialkylnaphthalene and polyalkylnaphthalene. Examples of the ester oil include diesters such as dibutyl sebacate, di-2-ethylhexyl sebacate, dioctyl adipate, diisodecyl adipate, ditridecyl adipate, ditridecyl glutarate, and methyl acetyl ricinolate, or trioctyl trimellitate. , Aromatic ester oils such as tridecyl trimellitate and tetraoctyl pyromellitate, and further trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol belargonate, etc. Polyol esters, and complex esters that are oligoesters of polyhydric alcohols and mixed fatty acids of dibasic acids and monobasic acids are also included. Examples of the ether oil include polyglycols such as polyethylene glycol, polypropylene glycol, polyethylene glycol monoether, and polypropylene glycol monoether, or monoalkyl triphenyl ether, alkyl diphenyl ether, dialkyl diphenyl ether, pentaphenyl ether, tetraphenyl ether, mono Examples thereof include phenyl ethers such as alkyl tetraphenyl ether and dialkyl tetraphenyl ether. Of these, ester oils and ether oils are preferred. In addition, synthetic lubricating oils such as tricresyl phosphate, silicone oil and perfluoroalkyl ether oil can also be used.

  When these are blended, care must be taken that the kinematic viscosity at 40 ° C. as the base oil falls within the above range.

  A thickener is blended with the base oil. This thickener comprises a fatty acid having 12 to 24 carbon atoms having a hydroxyl group in the molecule and a lithium salt of an aliphatic dicarboxylic acid having 2 to 12 carbon atoms. As the hydroxy fatty acid having 12 to 24 carbon atoms, the most preferable one is 12-hydroxystearic acid, but any other one can be used. Other examples that can be used include 12-hydroxylauric acid and 16-hydroxypalmitic acid. Moreover, as said C2-C12 aliphatic dicarboxylic acid, although azelaic acid is the most preferable, all other things can also be used. Other examples that can be used include sebacic acid, oxalic acid, malonic acid, succinic acid, adipic acid, pimelic acid, suberic acid, undecanedioic acid, and dodecanedioic acid. Here, the ratio of the C12-24 hydroxy fatty acid and the C2-12 aliphatic dicarboxylic acid is preferably 20-40% by mass of the C2-12 aliphatic dicarboxylic acid. When this ratio is less than 20% by mass or more than 60% by mass, a thermally stable thickener cannot be obtained, and the life of the grease composition at a high temperature cannot be realized.

  And the thickener used by this invention is obtained by making the said C12-C24 hydroxy fatty acid and C2-C12 aliphatic dicarboxylic acid react with lithium compounds, such as lithium hydroxide, for example. Such a thickener is generally called a lithium complex, and has a feature of superior heat resistance as compared with lithium soap. The blending amount of the lithium complex as a thickener in the grease composition is not particularly limited as long as the grease property is obtained, and is usually 5 to 35% by mass.

  In addition, tellurium dithiocarbamate and phosphate are added to the grease as essential additives. Both dithiocarbamate and phosphate esters of tellurium are extreme pressure agents, and the effect is further enhanced when used in combination. In addition, tellurium dithiocarbamate has a high effect of suppressing the generation of iron powder, and iron powder (iron ion) acts on the thickener to prevent the mixing consistency from increasing and is effective in stabilizing the grease. It is. Furthermore, it is possible to suppress so-called gritty or rough feeling caused by iron powder. In general, when an extreme pressure agent is added, the amount of evaporation of the base oil tends to increase. However, since the above base oil hardly evaporates, an increase in the amount of evaporation can be suppressed.

  Examples of the dithiocarbamate salt of tellurium include tellurium diethyldithiocarbamate, tellurium dibutyldithiocarbamate, and tellurium dimethyldithiocarbamate. The phosphate ester includes an acidic phosphate ester, a phosphite ester, an acidic phosphite ester, and the like, and examples thereof include diphenyl monodecyl phosphite, trioctyl phosphate, tricresyl phosphate, and the like.

  The blending amount of these essential additives is preferably about 0.5 to 10% by mass with respect to the total amount of grease. If the amount is less than 0.5% by mass, the effect cannot be obtained. On the other hand, when the blending amount exceeds 10% by mass, an improvement in the effect corresponding to the increase in the amount cannot be obtained, which is uneconomical, and the amount of the base oil or the thickener occupies a relatively small amount, thereby reducing the lubrication performance. .

  Greases include, for example, amine-based antioxidants, phenol-based antioxidants, sulfur-based antioxidants, antioxidants such as zinc dithiophosphate, benzotriazole, sodium nitrite, petroleum sulfonate, dinonylnaphthalene sulfate. Rust, sorbitan ester and other rust preventives, chlorine-based extreme pressure agents, phosphorus-based extreme pressure agents, zinc dithiophosphate, organic molybdenum and other extreme pressure agents, fatty acid, oil and vegetable oil and other oil improvers, metal deactivators, Additives commonly used in grease can also be added. In addition, the addition amount of these other additives will not be specifically limited if it is a grade which does not impair the objective of this invention.

The cross joint of the present invention is configured as described above, and comprises (a) a fatty acid having 12 to 24 carbon atoms having a hydroxyl group in the molecule and a lithium salt of an aliphatic dicarboxylic acid having 2 to 12 carbon atoms. A thickener, (b) a mineral oil having a kinematic viscosity at 40 ° C. of 300 to 500 mm ² / s, and a synthetic hydrocarbon oil having a kinematic viscosity at 40 ° C. of ²⁰ to 300 mm ² / s as essential components; Iron powder is generated by enclosing a grease containing a base oil having a kinematic viscosity at 40 ° C. of 60 to 200 mm ² / s, a dithiocarbamate salt of (c) tellurium and (d) a phosphate ester. Suppressed and drastically reduced roughness and roughness. Further, the grease is derived from the base oil, has high heat resistance, and suppresses the increase in consistency, so that it has excellent stability over time and is maintenance-free.

  In order to configure a steering device using the cross joint of the present invention, for example, if at least one of the three joints Jt1, Jt2, Jt3 as shown in FIG. Good.

  Further, as shown in FIG. 6, in the electric power steering apparatus, at least one of the two joints may be configured as the above-described cross shaft joint and connected to the telescopic shaft. The electric power steering device assists the squeezing force from the handle by the electric motor.

  The telescopic shaft is composed of a male shaft 41 and a female shaft 42 that are non-rotatable and slidably fitted to each other, as shown in a longitudinal sectional view in FIG. Further, as shown in FIG. 8 (a cross-sectional view taken along the line XX in FIG. 7), three shafts equally spaced on the outer circumferential surface of the male shaft 41 at intervals of 120 ° (phase) in the circumferential direction. A directional groove 43 is formed to extend. Correspondingly, three axial grooves 45 that are equally arranged at 120 ° intervals (phases) in the circumferential direction are formed to extend on the inner peripheral surface of the female shaft 42.

  Between the axial groove 43 of the male shaft 41 and the axial groove 45 of the female shaft 42, a plurality of rigid spherical bodies 47 (rolling bodies, which roll when the two shafts 41 and 42 move in the axial direction relative to each other). Ball) is installed to roll freely. The axial groove 45 of the female shaft 42 has a substantially arc-shaped cross section or a Gothic arch shape. The axial groove 43 of the male shaft 41 is composed of a pair of inclined planar side surfaces 43a and a bottom surface 43b formed flat between the pair of planar side surfaces 43a.

  A leaf spring 49 for contacting and preloading the spherical body 47 is interposed between the axial groove 43 of the male shaft 41 and the spherical body 47. As shown in a perspective view in FIG. 7B, the leaf spring 49 has a spherical body side contact portion 49a that contacts the spherical body 47 at two points, and a predetermined interval in the circumferential direction with respect to the spherical body side contact portion 49a. The groove surface side contact portion 49b contacting the planar side surface 43a of the axial groove 43 of the male shaft 1 and the spherical body side contact portion 49a and the groove surface side contact portion 49b are separated from each other. And a bottom portion 49d facing the bottom surface 43b of the axial groove 43. The urging portion 49c has a substantially U-shape and is bent in a substantially arc shape. The urging portion 49c is elastic so as to separate the spherical body side contact portion 49a and the groove surface side contact portion 49b from each other. Can be energized.

  As shown in FIG. 8, three axial grooves 44 that are equally arranged at 120 ° intervals (phases) in the circumferential direction are formed on the outer peripheral surface of the male shaft 41 so as to extend. Correspondingly, three axial grooves 46 equally distributed at 120 ° intervals (phases) in the circumferential direction are also formed on the inner peripheral surface of the female shaft 42. A plurality of rigid cylindrical bodies 48 (sliding bodies) that slide between the axial grooves 44 of the male shaft 41 and the axial grooves 46 of the female shaft 42 when the shafts 41 and 42 move relative to each other in the axial direction. , A needle roller) is interposed with a minute gap. These axial grooves 44 and 46 have a substantially arc-shaped cross section or a Gothic arch shape.

  Further, as shown in FIG. 7A, a stopper plate 50 with an elastic body is provided at the end of the male shaft 41, and the spherical body 47, the cylindrical body 48, the plate are provided by the stopper plate 50 with an elastic body. The spring 49 is prevented from falling off. Further, since the lubricant is applied between the axial groove 43 of the male shaft 41, the axial groove 45 of the female shaft 42, the leaf spring 49, and the spherical body 47, when torque is not transmitted (when sliding) ), The male shaft and the female shaft can slide in the axial direction with a stable sliding load without rattling.

  In the telescopic shaft configured as described above, the spherical body 47 is interposed between the male shaft 41 and the female shaft 42, and the spherical body 47 is preloaded to the extent that the female shaft 42 does not rattle by the leaf spring 49. When the torque is not transmitted, rattling between the male shaft 41 and the female shaft 42 is prevented, and when the male shaft 41 and the female shaft 42 move relative to each other in the axial direction, a stable sliding load without rattling is provided. Slide.

  On the other hand, at the time of torque transmission, the leaf spring 49 is elastically deformed to constrain the spherical body 47 in the circumferential direction, and the three rows of columnar bodies 48 interposed between the male shaft 41 and the female shaft 42 are the main torque transmission. Play a role. For example, when torque is input from the male shaft 41, since the preload of the leaf spring 49 is applied in the initial stage, there is no backlash, and the leaf spring 49 generates a reaction force against the torque and transmits the torque. At this time, overall torque transmission is performed with the transmission torque and the input torque between the male shaft 41, the leaf spring 49, the spherical body 47, and the female shaft 42 balanced. As the torque further increases, the clearance in the rotational direction of the male shaft 41 and the female shaft 42 via the cylindrical body 48 disappears, and the subsequent increase in torque is transmitted via the male shaft 41 and the female shaft 42 to the cylindrical body. 48 communicates. Therefore, the play in the rotational direction of the male shaft 41 and the female shaft 42 can be reliably prevented and torque can be transmitted in a highly rigid state.

  The telescopic shaft can also be filled with the grease filled in the cross joint so that the generation of iron powder and the increase in consistency can be suppressed, and the heat resistance can be improved. The

The present invention will be further described below with reference to examples and comparative examples.
(Examples 1-2 and Comparative Examples 1-3)
Test greases were prepared by blending thickener, base oil and additives as shown in Table 1. As Comparative Example 3, a commercially available extreme pressure grease was prepared. Then, each test grease of Example 1, Example 2, Comparative Example 1 and Comparative Example 2 was applied on a SPCC plate to a thickness of 5 mm, and heated for 250 hours in a thermostat at 160 ° C. before and after heating. The amount of evaporation was measured. At the same time, the change in the penetration degree before and after heating was measured. The total oxidation after heating was also measured. Each measurement result is shown in Table 1.

  A comparison between Example 1 and Example 2 and Comparative Example 2 shows that the base oil contains a mineral oil having a kinematic viscosity defined in the present invention and a synthetic hydrocarbon oil, and a lithium complex soap as a thickener. Has a low evaporation loss, little change in consistency, and low total oxidation, indicating that it has excellent durability at high temperatures. Moreover, it turns out that total oxidation is further improved by adding the additive (extreme pressure agent) prescribed | regulated by this invention.

  Moreover, the high speed high temperature bearing durability test was done about each test grease of Example 1, Example 2, the comparative example 1, and the comparative example 2. FIG. That is, 2.0 g of each grease is sealed in a tapered roller bearing (nominal number: 30205), and continuously rotated under the conditions of 6800 rpm of inner rotation, 120 ° C. of the outer ring temperature of the bearing, 980 N of radial load, and 1470 N of axial load. When the temperature exceeded 130 ° C. or when the motor overcurrent was reached, it was regarded as the burn-in life, and the time until that time was obtained. The results are shown in Table 1, and it can be seen that the tapered roller bearing in which the test grease of the example is sealed is superior in high temperature durability performance compared to the tapered roller bearing in which the test grease of the comparative example is sealed.

  Further, with respect to each of the test greases of Example 1, Example 2, Comparative Example 1 and Comparative Example 3, the roughness sensitivity evaluation was performed. In other words, a needle bearing for a steering device filled with each test grease is incorporated in the steering device, a 3 kg inertial panel is attached to one of the steering devices set at a joint angle of 30 °, and rotation of ± 180 ° from the other is 1 million cycles After the test (after endurance), the test drive was carried out on an actual vehicle. The same test drive was performed before the endurance. And “◎” when the steering feel is smooth. The case where there was a rough feeling was evaluated as “◯”, the case where there was a rough feeling was evaluated as “Δ”, and the case where there was a feeling of crunch was evaluated as “×”. The results are shown in Table 1. In particular, when the test grease of Example 1 was used, there was no initial rough feeling and excellent durability was obtained. Also, good results were obtained for the test grease of Example 2. On the other hand, when the test grease of Comparative Example 1 is used, since the needle bearing and the spider shaft portion are fitted to each other by a squeeze fitting, a crease occurs, and the sensation is eliminated from the rust and wear due to durability. There was still a feeling of roughness. In addition, when the test grease of Comparative Example 3 was used, the extreme pressure agent was effective in fitting to the nip, but the durability was poor.

(Example 3 and Comparative Example 4)
Test greases were prepared by blending thickeners, base oils and additives as shown in Table 2. At this time, the kinematic viscosities of the mineral oil and the synthetic hydrocarbon oil constituting the base oil were not specified, and the base oil kinematic viscosity after mixing was adjusted to the values shown in Table 1. Then, the following tests were performed on each test grease.
(Iron powder mixed heating test)
When grease mixed with iron powder is heated, the penetration of the grease increases due to the adverse effects of iron powder (iron ions). Therefore, the difficulty of being adversely affected by iron powder (iron ions) was evaluated based on the amount of increase in the mixing penetration before and after heating. First, 20 g of test grease was taken in a 50 ml beaker, and 2 wt% iron powder was added thereto and mixed. The mixture was allowed to stand at room temperature for 24 hours, and then the blending penetration (initial blending penetration) was measured. Next, this beaker was allowed to stand in a constant temperature bath at 100 ° C. for 24 hours, and then allowed to cool to room temperature, the blending penetration was measured, and compared with the initial blending penetration.
(Bearing rotating iron generation test)
A sealed deep groove ball bearing (nominal number: 608 VV) filled with 25% of the test volume of the space volume in a constant temperature bath at 80 ° C. with no radial load, an axial load of 98 N, and a rotational speed of 3600 rpm (rpm) Rotated for 300 hours. After the rotation, the outside of the bearing was cleaned and the enclosed test grease was dissolved in petroleum benzine and taken out. Then, the liquid was evaporated to dryness, and iron (iron powder generated by the rotation of the bearing) was collected.

  The results are shown in Table 2. It can be seen that the test grease of Example 3 has no increase in the penetration, and that the bearing in which the grease is sealed has suppressed the generation of iron.

It is a partial sectional view showing an example of a cross joint of the present invention. It is an enlarged view of the A part of FIG. It is a partial cross section figure which shows the other example of the cross-shaft coupling of this invention. It is a partial cross section figure which shows the other example of the cross-shaft coupling of this invention. It is the schematic which shows an example of a steering device. It is the schematic which shows an example of an electric power steering device. (A) Longitudinal sectional view of telescopic shaft and (B) Perspective view of leaf spring. FIG. 8 is a transverse sectional view taken along line XX in FIG. 7.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cross shaft coupling 2 Spider 3 Needle bearing 6 Axes 7, 8 Yoke 11 Bearing cup 12 Roller 14 Spider shaft part 18 Bearing hole 19 Buffer part

Claims (1)

In the cross shaft joint having a configuration in which the spider is fitted to the yoke by rotatably fitting the spider shaft portion to the bearing hole of the yoke via a bearing including a bearing cup and a plurality of rollers in the bearing cup. ,
(A) a thickener composed of a fatty acid having 12 to 24 carbon atoms having a hydroxyl group in the molecule and a lithium salt of an aliphatic dicarboxylic acid having 2 to 12 carbon atoms; and (b) a kinematic viscosity at 40 ° C. of 300. and mineral oil 500 mm ² / s, comprising as essential components a synthetic hydrocarbon oil having kinematic viscosity of 20 to 300 mm ² / s at 40 ° C., and, based on kinematic viscosity at 40 ° C. is 60~200mm ² / s A cross joint comprising a grease containing oil, (c) tellurium dithiocarbamate, and (d) a phosphate ester, enclosed in the bearing.

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